resolveIncomingOperationArgumentFields(cascading.flow.planner.Scope incomingScope)
Method resolveIncomingOperationArgumentFields returns the Fields outgoing from the previous FlowElement that
are consumable by this FlowElement when preparing Operation arguments.

resolveIncomingOperationPassThroughFields(cascading.flow.planner.Scope incomingScope)
Method resolveIncomingOperationPassThroughFields returns the Fields outgoing from the previous FlowElement that
are consumable by this FlowElement when preparing the Pipe outgoing tuple.